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Protoceratops
Protoceratops (meaning 'First Horned Face', derived from Greek proto-/πρωτο-'' 'first', ''cerat-/κερατ-'' 'horn' and ''-ops/-ωψ face) is a genusof sheep-sized (1.5 to 2 m long) herbivorous ceratopsian dinosaur, from the Upper Cretaceous Period (Campanian stage) of what is nowMongolia. It was a member of the Protoceratopsidae, a group of early horned dinosaurs. Unlike later ceratopsians, however, it lacked well-developed horns and retained some primitive traits not seen in later genera. Description Protoceratops was a quadrupedal dinosaur that was partially characterized by its distinctive neck frill at the back of its skull. The frill itself contained two large parietal fenestra (holes in the frill), while its cheeks had large jugal bones.2 The exact size and shape of the neck frill varied by individual; some specimens had short, compact frills, while others had frills nearly half the length of the skull. The frill consists mostly of the parietal bone and partially of the squamosal. Some researchers, including Peter Dodson3 attribute the different sizes and shapes of these bones to sexual dimorphism, as well as the age of the specimen, at the time of death. Protoceratops was approximately 1.8 meters (6 ft) in length and 0.6 meters (2 ft) high at the shoulder. A fully grown adult would have weighed less than 400 pounds (180 kg).4 Smaller specimen are estimated at 23 kilograms (51 lb).5 The large numbers of specimens found in high concentration suggest that Protoceratops lived in herds.4 Protoceratops was a relatively small dinosaur with a proportionately large skull. Protoceratops appears to have had muscular jaws capable of a powerful bite. These jaws were packed with dozens of teeth, well suited for chewing tough vegetation.4 The skull consisted of a massive frontal beak, and four pairs of fenestrae (skull openings). The foremost hole, the naris, was considerably smaller than the nostrils seen in later genera. Protoceratops had large orbits (the holes for its eyes), which measured around 50 millimeters in diameter.3 Behind the eye was a slightly smaller fenestra, known as the "infratemporal fenestra." Discovery and species Photographer J.B. Shackelford discovered the first specimen of Protoceratops in the Gobi desert, (Gansu, Inner Mongolia), as part of a 1922 American expedition looking for human ancestors. No early human fossils were found, but the expedition, led by Roy Chapman Andrews, collected many specimens of the Protoceratops genus, along with fossil skeletons of theropods Velociraptor, Oviraptor, and ceratopsid Psittacosaurus.3 Walter Granger and W.K. Gregory formally described the type species, P. andrewsi in 1923, the specific name in honor of Andrews. The fossils hail from the Djadochta Formation and date from the Campanian stage of the Upper Cretaceous (dating to between 75 and 71 million years ago).6 Researchers immediately noted the importance of the Protoceratops finds, and the genus was hailed as the "long-sought ancestor of Triceratops.3 The fossils were in an excellent state of preservation, with even the sclerotic rings (delicate occular bones) preserved in some specimens.3 In 1971, a fossil was found that captured a Velociraptor mongoliensis clutched around a Protoceratops andrewsi in Mongolia. It is believed that they died simultaneously, while fighting, when they were either surprised by a sand storm or buried when a sand dune collapsed on top of them. Paleobiology Category:Dinosaurs Category:Cretaceous dinosaurs Category:Ceratopsians Category:Dinosaurs of Asia